Metal cutting rod and process



June 13, 1950 F. G. DANHIER METAL CUTTING ROD AND PROCESS 3 Sheets-Sheet1 Filed Nov. 1'7, 1947 June 13, 1950 F. e. DANHIER METAL CUTTING ROD ANDPROCESS s Sheets-Sheet 2 Filed Nov. 17, 1947 Patented June 13, 1950UNITED STATES PATENT OFFICE assignor to La Soudur e Electrique Autogene,

Societe Anonyme, Brussels, Belgium Application November 17, 1947, SerialNo. 786,408 In Belgium January 16, 1945 6 Claims. 1

The cutting of iron and steel by oxidation by means of an oxygen jet,the reaction of oxidation being started and maintained by the heatdeveloped by an electric arc is a. well known process.

The present application is a continuation-inpart of my copendingapplication, Serial No. 597,- 508, filed in the United States June 4,1945, based upon a convention date in Belgium of January 16, 1945, nowabandoned.

Generally the oxygen was supplied through a hollow carbon electrode, theare being struck between the extremity of the electrode and the piece tobe cut. This old process had also been improved by the adjunction of analuminum rod as a flux.

It has also been known to cut metals under water by a hollow metallicrod through which an oxygen jet is passed, employing on the rod acarbonaceous coating which produces an envelope of gas.

It could also have been proposed to use, as a hollow electrode, a simplesteel pipe, in which the oxygen stream passes and to cause the electricarc to be struck between the extremity of the pipe and the piece to becut. This process would not be able to be developed industrially:firstly, on account of the great consumption of oxygen and pipes, withthe resulting frequent interruption of the cutting operation to changethe electrode, and especially because the slot or cut obtained would bevery wide.

After many experiments the applicant has finally realized a processgiving practical and unimpeachable results, in which no commercial pipesare used, but which consists in utilizing an oxygen jet through an innerpassage reserving in a metal electrode, with respect to a given totalcross section of said electrode, a greater metal section, so that for asufficient strength of the electric current, a minimum of electrodelength is consumed in the time unit for a maximum cutting length.

In other words, in the process according to the invention, an electrodeof given and necessarily limited length, but responding to the abovedefined condition, makes it possible to operate a cutting of relativelygreat length, all conditions inner passage for the oxygen gas in form ofone or several narrow channels, the total cross section of which in thepreferred embodiment is smaller than the quarter of the net metal crosssection of the electrode.

It has been found that the best ratio of the cross section of thepassage for the oxygen to the total cross section of the metal and boreof the rod is between 4 and 20 per cent.

An important aspect of the invention is the character of coating whichis employed to facilitate the cutting and minimize the consumption ofrods. In accordance with the invention the coating which surrounds orextends along the metallic core of the rod consists practically entirelyof inorganic ingredients which in the arc in the presence of oxygen formpractically only products which are solid or liquid if considered atroom temperature. This avoids the undesirable efiects of substantialevolution of fixed gases such as are obtained from conventional weldingrod coatings and from the underwater cutting rod coatings.

The drawings show a few only of the numerous embodiments in which theinvention may appear, the forms shown having been chosen from thestandpoints of convenience in illustration, satisfactory operation andclear demonstration of the principles involved.

Figures 1 to i inclusive are enlarged diagrammatic cross sections ofmetal cutting rods in accordance with the invention.

Figures 8 and 9 are diagrammatic sectional illustrations of the cuttingoperation.

In carrying the invention into effect, the combustible metal electrodemay be made of iron, for instance cast iron, but it can also be made ofsteel.

In a special embodiment, the oxy-electric cutting electrode according tothe invention is made, for instance, of a steel strip or band 20 foldedone or several times on itself and suitably compressed or drawn, in sucha manner that one inner channel 2| (Figure 1) or several inner channels22 (Figure 2) for the passage of the oxidizing gas (preferably at leastcommercially pure oxygen) will be formed.

Comparative tests have shown that for an equal area of the cross sectionof the passage for the oxygen and provided the above specified relationbetween the metal to be burned and the oxygen passage is maintained,good results can be obtained with various forms of passage cross sections other than the circular form, especially with passages oftriangular cross section'as shown at 23 (Figure 3).

For preventing the displacement of the arc at the extremity of the rodforming the gas electrode, the single or multiple channel may bedistinctly eccentric with respect to the section of the electrode as at2i or 25, in order to leave on one side a bigger mass of metalsupporting the electric arc (Figures 4 and 5).

The bore may also take the form of two triangular longitudinal passages28 as shown in Figure 6.

The core is surrounded by a coating 21 as shown in Figures 1 to '7,which performs a number of different functions as later explained. Inaccordance with the invention the coating is of mineral type and differsfrom the conventional arc-welding mineral coatings in that it consistspractically entirely of inorganic ingredients which in the arc in thepresence of oxygen form practically only products which are solid orliquid if considered at room temperature. In other words, the coatingdoes not evolve substantial quantities of fixed gases such as carbonmonoxide, carbon dioxide or the like which are so generally desired andwidely used to surround arc-welding operations and are accordinglyformed from ingredients included in conventional arc-welding coatings.The presence of such fixed gases in the cutting operation in accordancewith the present invention definitely slows up the cutting by dilutingthe stream of at least commercially pure oxygen which passes through thearc, thereby reducing the calorific intensity of combustion of the rodand work, and also carries away sensible heat needlessly in such fixedgases. ponents of the combustion of the rod of the present inventionwill be limited to vapors of metals, silicon, etc., which may be formedin the arc, and minor contents of vapor or gas from water or otherimpurities which may be unintentionally or undesirably present.

In the underwater cutting rods substantial amounts of carbonaceousmaterial have been included in the coatings so that any mineral, ifpresent at all, was not effective in aiding cutting. The coating of thepresent invention is for all practical purposes entirely mineral,providing a heavy liquid or solid which is projected forward by the arcand the oxygen stream into the cut. This stream of mineral from thecoat- 5 ing aids cutting in a number of respects. Many of the alloys outsuch as chromium alloys, form refractory oxides at thesurface of the cutand thus tend to form a refractory skin which impedes further cutting.When carbonaceous and chromium oxide, and also a chemical fiuxing actionexerted particularly by silicates and the like in the coating.Furthermore solid products of combustion result from the burning of thecore and work in the oxygen stream, and these tend to clog the kerf,whereas the mineral ingredients from the coating aid in fluxing awaysuch products of combustion. The net effect of the mineral coating is toproduce a much narrower kerf than would be possible were a carbonaceouscontaining coating used as in the In general the gaseous com- Ell priorart practice with underwater cutting or the conventional arc-weldingpractice.

There is a tendency also for the oxygen stream and. the arc to projector propel metal from the rod into the work, and the propulsion of thismetal stream also contributes to the propulsion of the coating productsand has a tendency to break up the refractory oxide skin and carry awayproducts of combustion from the kerf.

A further important function which will be emphasized in considerationof Figures 8 and 9 is the effect of the coating in sealing the oxygenjet to the work and forming a crucible, since the .core of the rod willburn out more rapidly than the mineral type coating.

The oxygen jet exerts substantial cooling effect and has a markedtendency to extinguish the are even when direct current is used. It is,therefore, very desirable on direct current, and most important onalternating current, to include an ionizing substance in the coating, tostabilize the arc and prevent extinguishing of the arc notwithstandingthe effect of variation in the arc length and of the oxygen jet.

The coated rod of the present invention, unlike the underwater cuttingrods, is capable of effective use in air with alternating current.

The coating also performs an important function of insulating the coreat all times. For example, in piercing it insulates the side wall fromthe edge of the hole being pierced. Likewise when cutting isaccomplished in a space close to side walls, the coating insulates fromsuch side walls. Furthermore, the coating insulates from the kerf wallsin deep cutting of thick'members, and permits re-establishing the are atthe bottom of the kerf when several rods are used in a single cut. Dueto the fact that the core burns off more rapidly than the coating, thecoating automatically holds a suitable arc spacing, and it is merelynecessary for the operator to hold the end of the coating in contactwith the work at all times. Thus there is in ordinary cutting noconscious effort involved in holding the are.

To summarize some of the important effects of the coating of theinvention, it will be seen that it aids in cutting by removingrefractory oxide and by fiuidifying combustion products, by sealing theoxygen jet to the work, and by stabilizing the arc in the presence ofoxygen and particularly on alternating current. The are stabilizingeffect is evident in spite of the use of low currents, which arefavorable for slower combustion of the rod.

When the electrode according to the invention is, for instance,constituted by a steel band or ribbon simply formed into a roll, so asto form a single narrow channel for the passage of the oxygen gas underpressure, this coating may also serve the purpose to secure thetightness of the electrode channel at 28 (Figure 7). Figure '7 issimilar to Figure 7 except that the bore is eccentric in Figure 7 andconcentric in Figure 7 The coating will be made from inorganicmaterials, a wide variety of which are suitable. Inorganic materialssuch as the carbonates which under the arc in oxygen yield a materialwhich is gaseous at ordinary room temperature should be avoided, andlikewise carbonaceous combustible materials such as cellulose should beeliminated. I Suitable coating materials include silicates of' calcium,magnesium, potassium, sodium, zirconium and iron and complex silicatesof two or more of the same, titanates of potassium, sodium, strontiumand iron; metallic oxides such as titanium dioxide (rutile) manganesedioxide, and magnetite; silicate glasses such as alkaline powderedsilicate glass; monazite sand (cerium phosphate), clay in minorproportions to aid extrusion or in larger proportion to act as a fluxand oxidizable metal powders with insulating ingredients.

Of the materials referred to, it is preferable to include an ionizer ineach coating. Suitable ionizers are potassium titanate, titaniumdioxide, manganese dioxide, potassium zirconium silicate, sodiumsilicate, calcium silicate and potassium silicate.

It will also be desirable to include a flux such as one of the silicatesor silica.

It will also be desirable to include in the coating a conductor of thesecond class which will be insulating at moderate temperature andtherefore will permit the coating to be insulating except at the hotend, and will be conducting in the hot end to aid in re-establishing thearc by bringing the hot end of the coating in contact with the work.Suitable conductors of the second class are ilmenite and magnetite.

The following are examples of coating compositions which are suitable touse with a core of iron, steel or stainless steel for cutting iron,steel, stainless steel, high chromium and high nickel alloys, brass,bronze and other ferrous and nonferrous structural metals and alloys.

ExampleI Per cent Magnetite Wollastonite Anhydrous clay Potassiumtitanate Potassium silicate 12 In this case the magnetite acts as aconductor of the second class as well as a flux, and the wollastoniteacts as an ionizer and a flux, while the potassium titanate acts as anionizer.

Example II Per cent Ilmenite Potassium zirconium silicate Powderedsilicate glass Anhydrous clay Sodium silicate Here ilmenite acts as aconductor of the second class and a flux, potassium zirconium silicate,powdered silicate glass and sodium silicate act as 6 Example IV Per centMagnetite 44 Rutile 31 Powdered silicate glass 13 Potassium silicate 12In this case magnetite acts as a conductor of the second class and aflux, and the remaining ingredients act as ionizers and fluxes.

It will be evident, of course, that other coatings may be made up usingentirely other inorganic materials which will not form any product whichis gaseous at room temperature.

The operation will be better understood by reference to Figures 8 and 9which show an electric-arc oxygen open air metal cutting rod 30 havingan interior bore 3i through which at least commercially pure oxygen ispassing under suitable pressure (for example 5 to 200 p. s. i.) andsuitable rate of flow. The bore is formed in the interior of a core 20in this case of steel, preferably of plain carbon low-carbon grade. Theoutside of the core is provided with a coating 32 surrounding the core.The coating is entirely inorganic and free from materials which wouldproduce products which are gaseous at room temperatures. An arc 33 hasbeen established at the end in contact with a metal plate or other work34 which is being cut. The metal plate or other work here shown may beiron, steel, stainless steel, high chromium or high nickel alloy, brass,bronze or the like. The direction Of travel of the rod 35 is from rightto left and a kerf 36 has been formed in cutting through the plate.Serrations 31 on the edge of the kerf are typical of the very slightirregularities which may be produced. The are acting at 39 has burnedaway the core more rapidly than the coating and more rapidly at thecenter 40' than at the edge. The coating then extends beyond the core atthe end at 4!, and portions of the core at 42 and the coating at 43 aremelted and projected forward into the cut, tending to cut away theleading edge 44 and carry oxide, slag and molten metal away from thecombustion zone 45 in globules 46. The surface pre-heated by the arealone is shown at 47 and the layer pre-heated by the arc and combustionof the core is shown at 48. The products of the combustion aresubstantially entirely solid or liquid at room temperature, sincesubstantially no carbonaceous material is available in the coating andthe carbon in the Work will ordinarily be a negligible factor. It willbe noted that the coating aids in the cutting by removing the skin ofrefractory oxide which forms on the leading edge and by carrying awayproducts of ,cbmbustion through erosion and fluxing. As shown, thecoating seals the jet around the are at 4|, preventing loss of gas andloss of heat. Coating also as shown at 4| automatically tends torestrict and concentrate the arc and in case of piercing or contact withwalls of the work at the side will prevent undesired side arcing.

Thus as shown, a metallic arc with direct or alternating current isestablished to the work, a stream of oxygen is passed through theinterior of the arc to the work, and the mineral coating consistingpractically entirely of inorganic ingredients, which in the arc in thepresence of oxygen form practically only products which are solid orliquid if considered at room temperature,

electrodes.

the cutting into the layers of the stack beyond the first layer is notpresent. In this form the coating particles tend to carry the cutthrough the subsequent plates to and e and beyondthe gaps- 5 1 and 5-2.

The following comparative tests have been run using rods as follows:

1- The rod. of. the present invention.

2'. The: underwater cutting.v rod with a. Scotch tape coating accordingto Ronay U. S. Patent 2,410,461.

3.. A standard gas shielded arc-welding, electrode coating on. a. steeltubular core. 3a. A standard gas shielded arc-welding electrode coatingwith a, waterproof vinyl resin coating following- Jensen U. S. Patent2,394,550.

4.. A Complete. vinyl resin type coating following Jensen U. S. Patent2,394,550.

The rod according to the present inventionwas an open seamed tubularsteel core rod covered with a non-gas forming silicate type coating, asherein described.

All the other experimental rods were made with the same tubular metalliccore as that used for the rod of the present invention. The Ronay typerod was covered according to the procedure recommended. by the U. S.Navy for the preparation of Ronay type rods for underwater cutting,using Scotch tape of type. MES as recommended bythe Navy;

The Jensen type rod using a standard arc welding electrode coating'plusa waterproof vinyl resin coating was prepared in the manner of the rodsmanufactured for the U. S. Nav for underwater cutting. The standardwelding electrode formula USEdIfOI" the slag forming portion or thecoating was of the limestone type used for arc-welding This coatingproduces a gaseous shield to' protect the weld metal in its transferacross the arc and a protective slag toprotect-the weld bead; while itis cooling. The waterproof covering was a vinyl resin known as Ucilon(United Chromium Company)" reinforced with lime inthe manner recommendedby Jensen for producing underwater cutting rods.

The completely vinyl resin typeof covering according te 'Jensen wasprepared with the vinyl resin and lim-e mixture as recommended byJensen. The thicknesses were adjusted to give the most favorableperformance of this rod.

The four types of arc oxygen: cutting: rods above described were testedunder identicalconditions, but adjustments to produce the conditionsmost favorable to Ronay and Jensen were required. All cuts were made inopen air at normal room temperature. Oxygen was supplied from a standardtank through a reducing valve at '75 pounds per square. inch whencutting mild steel and at pounds per square inch (except for twoinstances at 20. pounds per square inch) when cutting. stainless steel.The current supplied to the arc was obtained from .a standard weldingsource. The direct current was supplied by a motor generator set and thealternating current was supplied by 7o were tested in stack cutting.

a. welding transformer. The current was approximately 200 amperes ineach test. The machine settings were identical in each case but becauseof different characteristics in the rods some operated on less currentthan others. As shown in the accompanying table the currents ranged fromto 208 amperes and the voltages varied from 28 to 50 volts, but most ofthe tests fell in the range from 160 to 200 amperes' and 30 to 35 volts.The materials out were A" thick mild steel plate, thick mild steelstrips stacked three high with a & air gap between the strips and /1"thick type 347 (18% Cr, 9% Ni, 1% Cb) stainless steel plates.

Cutting of mild steel The following, table shows. the result in cuttingmild steel:

GuttingData for 4" Mild Steel Rod CmrentRangcs Ave Burmofl 7 Speed,Ratio, Amps Volts V inlmin. in. cut/in.

1 Present invc 190-204 31-35 25. 4 1.19 2 Scotch tape 160-200 4450 22. 00. 96 3 Gas shielded"v 200 34 22.2 i 1.06 3a Gas shielded water prooied-Jensen 190-208- 29-34 17.4 0. 75 4 Allvinyl'resin-Jcnsen -208 28-35' l4.3 0'. 73

Under the conditions of these tests the rod of the present inventionshows definite superiority in. cutting mild steel. The speed in cuttingmild steelplate is 10. to. 77% faster than the speed with. othertypesof. rod The efiiciency of the. rod of the present invention as.measured by the distance cutper unit lengthof. rod is ID to 60% betterthan. the efficiency of the. other rods. The closest approach to the rodof the present invention in efiiciency is neither the Ronay nor Jensentypes but the gas shielded welding rod type of coating.

Cutting stainless steel As shown in the table, the rod. of the presentinvention was more rapid and more eflicient in cutting of type 347stainless steel than any ofthe other rods.

Staclc cutting Because of the unsatisfactory performance of the Jensentype rods on solid mild steel in open air, only the rodof thepresentinvention, the rodwith the gasshielded mineral type weldingrodcoating and the Scotch tape Ronay type rod thick and 2" wide mildsteel strips were stacked three high separated by /64" to leave two airgaps between the. three strips. Cuts were attempted while dragging therod across the upper surface of. the top strip as though the plate weresolid, but with both the Scotch tape and gas shielded rod it wasnecessary to work the rod down into the kerf to cut the lower pieces.The following results were obtained:

Cutting Data for Stack Cutting Rod Current Ranges Ave. Burn-oil Speedin./min.

Amps. Volts Present invention. Scotch tape-Ronay... Gas shielded ODNHNOW

With the rod of the present invention there was no trouble in stackcutting, the power of the arc-oxygen stream and the coating bridging thegaps with ease. The amperage and voltage were normal. With the gasshielded arc-welding type of coating without waterproof layers, theperformance was fair but the speed was definitely lower. The operatingamperage and voltage were normal. With the Scotch tape type of Ronaycoating, the performance was quite unsatisfac- 2 tory. The voltage andamperage swung violently from low to high values, so much so that thearc was extinguished briefly about seven times during seconds ofoperation. The speed of cutting was slow.

Alternating current Of all of the rods described the type of the presentinvention was far superior in operation 35 bined in obtaining theaverage speed and average burn-off rate of this rod. The rod with thegas shielded arc Welding type of coating was unsatisfactory foroperation with alternating current, since the arc was so unstable that asimple dragging operation was not possible and see-saw action wasnecessary to keep the are going. The same coating protected with theouter Waterproof layer according to the Jensen patent showed a stabilityof are increased only enough so that drag cutting was barely possible.The Ronay Scotch tape coating operated about as well with alternatingcurrent as with direct current but in each case it was unsatisfactory inopen air cutting. The operator experienced great difficulty inrestriking the are after the rod and the plate being cut became heatedsince the coating softened and burned off at the tip to expose the barecore which froze fast to the plate. Moderate overheating caused theScotch tape coating to soften and be blown completely 01f the rod.

The presence of gas forming ingredients in these other coatings isbelieved to be an essential reason for the deficient behavior in thetests de scribed. The completely inorganic character of the coating ofthe present invention is of significant importance in accomplishingstack cutting.

in view of my invention and disclosure variations and modifications tomeet individual whim or particular need will doubtless become evident toothers skilled in the art, to obtain all or part of the benefits of myinvention without copying the structure and process shown, and Itherefore claim all such insofar as they fall within the reasonablespirit and scope of my claims.

Having thus described my invention what I 7 claim as new and desire tosecure by Letters Patent is:

1'. An electric-arc oxygen open-air metal cutting rod comprising atube-like metallic core having an interior longitudinal oxygen bore anda mineral non-oxygen-liberating type coating, fusible in the cuttingare, supported on and extending longitudinall along the core and thecoating consisting practically entirely of inorganic ingredients whichin the arc in the presence of oxygen form practically only productswhich are solid or liquid if considered at room temperature, the coatingcomprising an ionizing substance.

2. An electric-arc oxygen open-air metal cutting rod comprising atube-like metallic core having an interior longitudinal oxygen bore anda mineral non-oxygen-liberating type coating, fusible in the cuttingare, supported on and extending longitudinally along the core and thecoating consisting practically entirely of inorganic ingredients whichin the arc in the presence of oxygen form practically onl products whichare solid or liquid if considered at room temperature, the coatingcomprising a conductor of the second class.

3. An e1ectric-arc oxygen open-air metal cutting rod comprising atube-like ferrous metal core having an interior longitudinal oxygen boreof diameter between 4 and 25 percent of the net metal cross section anda mineral non-oxygenliberating type coating, fusible in the cutting arc,surrounding the core and consisting practically entirely of inorganicingredients which in the are in the presence of oxygen form practicallyonly products which are solid or liquid if considered at roomtemperature.

4. The process of cutting metal in open air, which comprisesestablishing an alternating current metallic are from a core to thework, passing a stream of oxygen in open air throu h the interior of thealternating current are to the work, fusing in the arc the core and anionizing mineral non-oxygen-liberating coating consisting practicallyentirely of inorganic ingredients which in the arc in the presence ofoxygen form practically only products which are solid or liquid ifconsidered at room temperature and projecting the fused products of thecoating and core into the out under the action of the arc and the streamof oxygen.

5. The process of stack cutting metal in the open air, which comprisesestablishing a metallic arc to a stack of work having gaps between thework and directed across the stack, passing a stream of oxygen throughthe interior of the are directed against the stack in the directionacross the stack, fusing in the are a mineral non-oxygenliberatingcoating consisting practically entirely of inorganic ingredients whichin the arc in the presence of oxygen form practically only productswhich are solid or liquid if considered at room temperature, ionizingthe coating in the arc and projectin the fused products of the coatinginto the cut and across the gaps of the stack to cut across such gaps.

6. The process of stack cutting metal in the open air, which comprisesestablishing an alternating current metallic arc to a stack of workhaving gaps between the work and directed across the stack, passing astream of oxygen through the interior of the are directed against thestack in the direction across the stack, fusing in the are a mineralnon-oxygen-liberatin coating consisting practically entirely ofinorganic ingredi- 2,510,960 12 ents which in the are in the presence ofoxygen REFERENCES CITED form practically only product's whicharesoltdior The following references are of record in the liquidif-considered at room temperature, ionizing me of this patent: thecoating to maintain the arc in the presence of the oxygen stream and ofthe alternating cur- 5 UNITED STATES PATENTS rent and projecting thefused products of the Number Name Date coating across the gaps of thestack tocut across 1,321 ,309 Holslag Nov. 11, 1919 such gaps. 1,451,392Holslag Apr. 10, 1923 FR'ANQOIS GEORGES .DANHIER. 2,394,550 Jensen Feb.12, 1945

